Scientists create first stable semisynthetic organism

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Life’s genetic code has only ever contained four natural bases. These bases pair up to form two “base pairs”—the rungs of the DNA ladder—and they have simply been rearranged to create bacteria and butterflies, penguins and people. Four bases make up all life as we know it.

Until now. Scientists at The Scripps Research Institute (TSRI) have announced the development of the first stable semisynthetic organism. Building on their 2014 study in which they synthesized a DNA base pair, the researchers created a new bacterium that uses the four natural bases (called A, T, C and G), which every living organism possesses, but that also holds as a pair two synthetic bases called X and Y in its genetic code.

TSRI Professor Floyd Romesberg and his colleagues have now shown that their can hold on indefinitely to the synthetic base pair as it divides. Their research was published January 23, 2017, online ahead of print in the journal Proceedings of the National Academy of Sciences.

“We’ve made this semisynthetic organism more life-like,” said Romesberg, senior author of the new study.

While applications for this kind of organism are still far in the future, the researchers say the work could be used to create new functions for single-celled that play important roles in drug discovery and much more.

Building a Unique Organism

When Romesberg and his colleagues announced the development of X and Y in 2014, they also showed that modified E. coli bacteria could hold this synthetic base pair in their genetic code. What these E. coli couldn’t do, however, was keep the base pair in their code indefinitely as they divided. The X and Y base pair was dropped over time, limiting the ways the organism could use the additional information possessed in their DNA.

“Your genome isn’t just stable for a day,” said Romesberg. “Your genome has to be stable for the scale of your lifetime. If the semisynthetic organism is going to really be an organism, it has to be able to stably maintain that information.”

Romesberg compared this flawed organism to an infant. It had some learning to do before it was ready for real life.

In stepped TSRI Graduate Student Yorke Zhang and Brian Lamb, an American Cancer Society postdoctoral fellow in the Romesberg lab at the time of the study. Together, they helped develop the means for the single-celled organism to retain the artificial base pair. Read more at: https://phys.org/news/2017-01-scientists-stable-semisynthetic.html#jCp

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